Electro active compression bandage

ABSTRACT

The proposed device includes two segments adapted to enclose a body part in a form-fitting manner. Each segment contains an electroactive-material-based actuator, which is adapted to receive an electrical control signal and in response thereto adjust the actuator&#39;s morphology, so as to cause the segment to apply a basic pressure profile to the body part. A pressure transition is adapted to redistribute the basic pressure profiles between the first and second segments. A control signal in respect of the first segment causes the pressure transition system to apply a first adjusted pressure profile to at least part of the second portion of the body part, and vice versa, a control signal in respect of the second segment causes the pressure transition system to apply a second adjusted pressure profile to at least a part of the first portion of the body part.

This application is a divisional application of the national stage entryof PCT Application No. PCT/EP05/10886 filed on Oct. 10, 2005, now U.S.Pat. No. 7,857,777, which claims priority to EPO4445108.6 andEPO4445107.8, both filed Oct. 11, 2004, and each of which are herebyincorporated by reference in their entirety.

THE BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention relates generally to the application of pressureprofiles to living tissues. More particularly the invention relates to adevice for exerting an external pressure to a human body part and to atherapeutic garment.

External pressure profiles may be applied to living tissues, e.g. of aperson's limb, in order to attain various effects with respect to thesetissues. Perhaps the most well known example is the so-called G-suitworn by a pilot to restrict the blood circulation in his/her lower bodyparts under certain conditions, and thus reduce the risk that aninsufficient amount of blood is fed to the pilot's head.

However, also in the medical field there are many examples of situationsin which it is relevant/desirable to apply an external pressure to apart of the human body, in order to cure or mitigate a disease orcondition. For instance, lymphoedema is a condition where the lymphaticsystem of a patient has been compromised, thereby resulting in a buildupof lymphatic fluids and proteins in one or more extremities. So far,various approaches have been attempted to control the swelling of theafflicted extremities. The compression-based treatment of lymphoedema isprimarily dealt with in three ways, which may be combined to achieve animproved result, compression bandaging, pneumatic compression pumps andmassage. The compression bandaging may be further divided into twogeneral approaches: multi-layered lymphatic bandaging and elasticcompression garments/bandages. Both these methods are used to staticallycompress the afflicted limbs, whereas pneumatic compression pumps andmassage represent dynamic treatments.

Multi-layered lymphatic bandages are applied to a patient in order toreshape one or more of the patient's limbs. The bandages consist ofabsorbent layers, padding and short-stretch bandages. The absorbentlayers must be custom made by a technician to fit the patient. Moreover,the underlying pressure is unknown after application, and the bandagesare there to prevent the limb from further expanding and to breakupproteins with the help of patient movement. Nevertheless, these bandagesare associated with numerous problems. During the treatment the bandagesmust be adjusted many times, for example because the bandages have astatic shape and the shape of the limb varies over time. The bandagesare also bulky and hot to wear due to the many layers applied to thelimb, and therefore the bandages cannot be worn under clothing.Naturally, the therapy for the patient is limited in that themulti-layered lymphatic bandages cannot actively pressurize the body.

Elastic compression bandages are used to statically pressurize anafflicted limb. Here, a caregiver wraps the afflicted limb with acombination of elastic bandages and absorbent layers. The bandages arearranged so as to apply a graduated pressure to the limb. The pressuregradient along the limb is structured such that the highest pressure isat the distal end, and the lowest pressure is located at the proximalend of the limb. Hence, also in this case, the pressure application isstatic and a qualified person must apply the bandages to ensure that anappropriate pressure is accomplished, particularly since there is noconvenient way to accurately measure the pressure applied to the limb.Normally, a constant bandage tension is applied while wrapping the limb,and the pressure graduation is typically a consequence of the limb beingthinner at the distal part than at the proximal part. As the limbchanges size due to the pressure, and as the bandages creep, thepressure application will decrease. This is true already within hours ofapplying the bandages.

A pneumatic compression pump device is used to dynamically pressurizelimbs of patients. Here, dynamic pressurization is employed both to pumplymphatic fluids from the limb in wave-like, or graduated, pressureprofiles and to breakup proteins that collect and harden in theafflicted limb. To generate the wave-like and graduated pressureprofiles along the limb, a sleeve portion of the device must havemultiple chambers. Each chamber is pressurized at the appropriate timeas determined by the treatment prescription. However, the pneumaticcompression pump devices are relatively inefficient, and thereforecannot operate from batteries for any significant length of time. Infact, it is normally required that the device be connected to mainspower, and as a further consequence that the patient be stationaryduring the treatment. Since the pneumatic compression pump device isairtight, heat produced by the patient is accumulated in the device.Thus, the device can only be used for comparatively short durationsbefore it becomes too uncomfortable for the patient. Although the devicecan dramatically reduce edema during treatment, after use, staticcompression bandages (or equivalent) must be applied to prevent thefluids from draining back into the afflicted limb. Additionally, thedevice is noisy, the air-pressure measurements used to infer pressureapplied to the limb can be inaccurate, and unintentionally high pressurelevels may harm the patient.

A qualified massage therapist/clinician may also apply various forms ofmassage to a patient. Such massage techniques are highly technical andrequire significant training to perform. Thus, the outcome of thetreatment depends very much on the skill of the clinician.

U.S. Pat. No. 5,997,465 describes a device for exerting an externalpressure on a human body, wherein the device surrounds a body part witha comfortable fit. The device includes memory material components, whichalter their shape in response to an electric signal. Thereby, in acontracted state, these components may squeeze the body part, forexample to prevent pooling of blood in the body part of a pilot whensubjected to G-forces. Then, in a non-contracted state (i.e. when noelectric signal is present) the memory material components resume theiroriginal shape, and the squeezing ceases. The electrical controlproposed in this document overcomes some of the shortcomings associatedwith the above-described dynamic procedures, i.e. the pneumaticcompression pump devices and massage forms. However, the solution isstill inadequate for many medical applications. For instance, the skinof a patient is often compromised due to various medical conditions. Inaddition, the health of the patient's skin may lack elasticity, strengthand resilience. Therefore, extreme care must be given to ensure that thepressure profile applied to the patient is medically safe. For instance,if highly localized pressures are applied for long periods of time, thetissues can tear and/or pressure ulcers may be formed. Moreover, ifsubjected to repeated rubbing, the skin can chafe, or even rip.Additionally, the medical treatments often require that the garments beworn for prolonged periods of time during which pressure and/or repeatedpressure pulsation may be applied. Such activities further increase therisk of damage being caused to the patient's skin. Some medicalapplications may also require that the pressure profiles be variableover a very wide range, for example to promote fluid flow in superficialand interstitial tissues. Sometimes it is desired that the pressureprofile emulate the naturally occurring function of a healthy body part.

The document EP 1 324 403 describes a motion augmentation solution,wherein an electroactive elastic actuator assists a patient to bend orunbend a joint. Although the document also briefly touches upon massageapplications, there is no teaching or suggestion as how the actuators'pressure profiles may be modified, adjusted or by other means besmoothed out to meet various medical criteria.

The published U.S. patent application No. 2003/0212306 discloseselectroactive polymer-based artificial muscle patches to be implantedadjacent to a patient's heart. The document also describes artificialsphincters to be implanted around the urethra, the anal canal, or thelower esophagus. Thus, the solutions exclusively aim at body internalpressure applications. Naturally therefore, the pressure transitionissues are quite different from any implementations wherein pressuresare applied to the outside of the body. For example, inside the body,due to the absence of nerves the patient cannot normally feeldiscomfort. Instead, it is here more important to prevent tissue deathand calous formation near the edges of the patches.

U.S. Pat. No. 6,123,681 describes a polymer stocking for applyingcompressive forces to inhibit the development of thrombophlebitis.Interestingly, this document does not address the way in which pressureapplication is smoothed out over the limb. Instead, it appears mostlikely that the proposed polymer strips, which are relatively far spacedfrom one another risk to cause pressure ulcers and tissue damages.Moreover, improper materials are selected for the intended applicationbecause none of the polymer strips are capable of providing the highforces required in the thrombophlebitis treatment.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to alleviate theabove-mentioned problems and thus accomplish improved pressure profilesin terms of a well-defined location, distribution and magnitude of thepressure that is applied to the outside a human body part.

According to one aspect of the invention, the object is achieved by theinitially described device, wherein the device includes a pressuretransition system, which is located relative to the body part, the firstand second segments and has such mechanical properties that the pressuretransition system is adapted to redistribute the basic pressure profilesbetween the first and second segments. The pressure redistribution issuch that a control signal in respect of the first segment causes thepressure transition system to apply a first adjusted pressure profile toat least a part of the second portion of the body part, andcorrespondingly, a control signal in respect of the second segmentcauses the pressure transition system to apply a second adjustedpressure profile to at least a part of the first portion of the bodypart.

An important advantage attained thereby is that very flexible andwell-controlled pressure profiles may be accomplished, which are adaptedto suit the needs of various treatments. The proposed pressuretransition system also facilitates pressure application in regions ofthe body not amenable to direct application from actuators, e.g. elbowsand wrists. Thus, as a further consequence, patient mobility isfacilitated during treatment. Also individual patient needs may behandled, such as in cases where the skin is extremely vulnerable. Sincethe pressure profiles associated with each segment are smoothed out, sothat the patient senses relatively fuzzy pressures, the patient comfortduring the treatment is generally enhanced. More important, however, theefficacy of the treatment is improved across joints and othercomplicated body regions where actuators cannot directly apply pressure.

According to one preferred embodiment of this aspect of the invention, achange of the actuator morphology is instigated by the electricalcontrol signal. Moreover, each actuator is adapted to maintain a thuschanged morphology on the basis of an electrical control signal whichsupplies charge replenishment to the actuator. Consequently, it ispractically only necessary to add or remove charges when adjusting anactuator. The charge replenishment represents very small quantities ofenergy that compensate for charge leakage due to minor conductiveeffects in the electroactive-material. Since the altered morphologyremains also after that the control signal ceased, the inventionaccording to this embodiment is very power efficient, particularly withrespect to static or quasi-static pressure profiles.

According to another preferred embodiment of this aspect of theinvention, the pressure transition system is adapted to be positionedbetween the first and second segments when the device is fitted on thebody part. This location of the pressure transition system isadvantageous, since it enables pressure bridging between the segments.At the same time, the device may have a comparatively thin crosssection.

According to yet another preferred embodiment of this aspect of theinvention, the pressure transition system is adapted to be positionedbetween a first surface defined by the first and second segments and asecond surface defined by the body part. The pressure transition systemhere extends over the first and second portions of the body part whenthe device is fitted on the body part. Consequently, a pressure profilegenerated by the first segment may efficiently “leak over” to the secondportion of the body part via the pressure transition system, and viceversa.

Preferably the pressure transition system also has a low-frictionsurface towards the first and second segments. The surface is therebyadapted to allow a smooth tangential movement of the first and secondsegments relative to the pressure transition system. This design isadvantageous because it mitigates any undesired effects on the bodypart, such as friction, caused by relative movements created by thesegments' actuators.

According to still another preferred embodiment of this aspect of theinvention, the first and second segments are arranged such that aportion of the first segment covers a portion of the second segment whenthe device is fitted on the body part. Thereby, an alternative, orcomplementary, means is provided for accomplishing a pressure profileleak-over between different segments and to attain smoothed-out/fuzzypressure profiles.

According to another preferred embodiment of this aspect of theinvention, the pressure transition system includes a number ofcollapsible ribs, which are adapted to extend along a general centralaxis of the body part. The ribs are positioned between at least onesegment and a particular portion of the body part when the device isfitted on the body part. An actuator in each of the at least one segmentis adapted to cause a tangential movement of the segment relative to thebody part and the collapsible ribs are adapted to fold in response tothis movement, such that when folded the ribs exert a radial pressure onthe particular portion of the body part. Such a transformation between atangential movement and a radial pressure is desirable because it allowsa design with a very slim device profile.

Alternatively, or as a complement thereto, the pressure transitionsystem may include at least one flexible chamber, which is adapted to bepositioned between at least one of the segments and a particular portionof the body part when the device is fitted on the body part. An actuatorin each of the at least one segment is adapted to cause a tangentialmovement of segment relative to the body part, and the at least onechamber is adapted to transform this movement into a resulting radialpressure on the particular portion of the body part.

According to yet another preferred embodiment of this aspect of theinvention, the flexible chamber has an elastic wall of an anisotropicmaterial, and the chamber is arranged relative to the body part when thedevice is fitted on the body part, such that the chamber is relativelystretchable in a circumferential direction of the body part andrelatively stiff in a direction along a general central axis of the bodypart. Thus, any tension forces generated by the actuators mayefficiently be transformed into desired pressure profiles with respectto the body part.

According to still another preferred embodiment of this aspect of theinvention, the pressure transition system includes a number ofprotrusions adapted to be positioned between at least one of thesegments and a particular portion of the body part when the device isfitted on the body part. The protrusions, in turn, are adapted toconvert the basic pressure profile of the at least one segment into anon-uniform pressure profile to the particular portion of the body part.For example, the protrusions may be cylindrical bulges. However, theprotrusions may also include at least one rigid rib, which is adapted toextend along a general central axis of the body part when the device isfitted on the body part. Then, as the segment exerts a pressure profile,a respective peak pressure ridge is defined by a positioning of each ofthe at least one rib relative to the body part. Consequently, anincreased pressure can be attained at one or more desired areas.

According to yet another preferred embodiment of this aspect of theinvention, the device includes a control unit adapted to produce arespective control signal to each of segment. The control unit isadapted to vary the control signal over time, so that a particulartreatment profile is implemented with respect to the body part.Preferably, the treatment profile involves producing repeated cycles ofvariations between relatively high and relatively low basic pressureprofiles by means of each segment. Hence, the device may perform anintermittent compression therapy and/or adjust (e.g. increase) theapplied pressure gradually, and/or produce quasi-static pressureprofiles.

According to still another preferred embodiment of this aspect of theinvention, the pressure transition system includes a number of moisturepassages adapted to receive exudates from the body part. Furthermore,the moisture passages (e.g. in the cells of an open-celled foam) may beadapted to transport (or milk) any received exudates from the body partto one or more liquid receptacles concomitantly with the repeatingpressure cycles. Thereby, sweat can be removed from the patient's skinand exudates can be drawn from wounds.

According to another preferred embodiment of this aspect of theinvention, the pressure transition system includes a number of airchannels which are adapted to allow air to pass to the body part (e.g.via the cells of an open-celled foam). Preferably, also the air channelsare adapted to exchange air between the body part and a localenvironment outside the device concomitantly with the repeating pressurecycles to improve the ventilation of the patient's skin.

According to yet another preferred embodiment of this aspect of theinvention, the pressure transition system includes at least one sensorelement adapted to register a physiological parameter of the body part.A data signal reflecting this parameter is transmitted to the controlunit. Thereby, the control unit may survey and analyze the medicalcondition of the body part, and if necessary, trigger an alarm and/oralter the treatment profile.

According to still another preferred embodiment of this aspect of theinvention, the pressure transition system includes at least one sensorelement adapted to register a parameter expressing an environmentalcondition in proximity to the body part. A data signal reflecting thisparameter is transmitted to the control unit. Thereby, the control unitmay survey and analyze the environmental conditions for the body part,and if necessary, alter the treatment profile and/or trigger an alarm.

According to another preferred embodiment of this aspect of theinvention, the pressure transition system includes at least one pocketadapted to contain a drug substance. The pressure transition system isalso adapted to administer a transport of this substance to the bodypart. Thus, a pressure/massage treatment may be combined with a drugtherapy. The drug substance may also be an antibacterial agent, so thatthe risk of infections and other sanitation related conditions could bereduced.

According to yet another preferred embodiment of this aspect of theinvention, the drug substance is a gel adapted to perform athermotherapy on the body part (i.e. either cryotherapy or heattherapy). Moreover, the gel may be adapted to facilitate activation ofthe actuator. Namely, if the actuator is of a conducting-polymer type, agel-based electrolyte may both facilitate actuation of the actuator andaccomplish the thermotherapy.

According to other preferred embodiments of this aspect of theinvention, at least one of the actuators includes an electroactivematerial in the form of an electroactive polymer or ceramic, which iseither a field activated electroactive material adapted to operate basedon Maxwell stress effects, electrostrictive or piezoelectric effects, oran ionic electroactive material, for example a conducting polymer.Videlicet, due to their intrinsic characteristics, all these materialsenable very compact and slim device designs that are suitable for manypurposes, particularly within the medical field.

According to another aspect of the invention, the object is achieved bythe initially described therapeutic garment, wherein the garmentincludes at least one of the proposed devices. Of course, such a garmentis advantageous for the same reasons as the above-described device.

Hence, by means of the invention, a cost efficient solution is attainedfor applying an external pressure to a human body part, which also ishighly flexible. The invention may be optimized for various medicalpurposes, and for instance be used for treatment or prophylaxis oflymphoedema, deep venous thrombosis, venous leg ulcers, venousinsufficiency, arterial ulcers, arterial insufficiency, diabetic footulcers, cardiovascular diseases, claudication, burns and sportsinjuries. The proposed solution may also be used in stress therapy,massage therapy enhanced external counter pulsation therapy and bloodpressure monitoring.

Further advantages, advantageous features and applications of thepresent invention will be apparent from the following description andthe dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now to be explained more closely by means ofpreferred embodiments, which are disclosed as examples, and withreference to the attached drawings.

FIGS. 1 a-c show schematic cross-section views of devices according toembodiments of the invention,

FIGS. 1 d-e show schematic cross-section views of devices according tothe prior-art solutions,

FIG. 2 shows a perspective view of a device according to a firstembodiment of the invention,

FIG. 3 shows a side view of a device according to a second embodiment ofthe invention,

FIGS. 4 a-b show schematic cross-section views of a first embodiment ofa proposed pressure transition system,

FIGS. 5 a-b show schematic cross-section views of a second embodiment ofa proposed pressure transition system,

FIGS. 6 a-c show perspective views of further embodiments of theproposed pressure transition system,

FIG. 7 shows a cross-section view of the pressure transition systemaccording to a particular embodiment of the invention,

FIGS. 8 a-b illustrate a basic morphology of a planar field activatedEAM-based actuator according to one embodiment of the invention,

FIGS. 9 a-c illustrate the morphology of a cylindrical field activatedEAM-based actuator according to one embodiment of the invention,

FIGS. 10 a-b illustrate the morphology of a field activated EAM-basedactuator of multilayer type according to one embodiment of theinvention,

FIGS. 11 a-b illustrate the morphology of a field activated EAM-basedactuator of C-block type according to one embodiment of the invention,

FIGS. 12 a-b illustrate the morphology of a field activated EAM-basedactuator of bubble type according to one embodiment of the invention,

FIG. 13 shows a field activated EAM-based actuator of a first cymbaltype according to one embodiment of the invention,

FIGS. 14 a-b show a field activated EAM-based actuator of a secondcymbal type having a flexible interface to link mechanical energyproduced the actuator towards a body part according to one embodiment ofthe invention,

FIGS. 15 a-b illustrate a basic morphology of an ionic EAM-basedactuator according to one embodiment of the invention,

FIGS. 16 a-b illustrate the morphology of a bilayer ionic EAM-basedactuator according to one embodiment of the invention,

FIGS. 17 a-b illustrate the morphology of a triple ionic layer EAM-basedactuator according to one embodiment of the invention,

FIGS. 18 a-c show side and top views of a conducting polymer actuatoraccording to one embodiment of the invention,

FIGS. 19 a-b schematically illustrate the operation of a segment in adevice according to one embodiment of the invention which includesactuators of the type shown in the FIGS. 18 a-c,

FIGS. 20 a-b show side views of a bending actuator according to oneembodiment of the invention,

FIGS. 21 a-b schematically illustrate the operation of a segment in adevice according to one embodiment of the invention which includesactuators of the type shown in the FIGS. 16 a-b,

FIG. 22 schematically illustrates a devices according to one embodimentof the invention, and

FIGS. 23-26 illustrate examples of therapeutic garments including theproposed device.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 a shows schematic cross-section view of a device according to oneembodiment of the invention for exerting an external pressure to a humanbody part 100. The device includes a segment S1, which is adapted to atleast partially enclose the body part 100 in a form-fitting manner. Thesegment S1 contains a controllable active-material based actuator A1(e.g. of electroactive ceramics or polymer, conducting-polymer,carbon-nano-tube or electroactive-gel type) that in response to acontrol signal is adapted to cause the segment S1 to apply a basicpressure profile P1 to the body part 100. A pressure transition systemPTS of the device is adapted to redistribute this basic pressure profileP1 into an adjusted pressure profile P1 _(ad), which is different fromthe basic pressure profile P1. Thus, in response to a control signal inrespect of the segment S1, the adjusted pressure profile P1 _(adj) isapplied to the body part 100.

According to one embodiment of the invention, the pressure transitionsystem PTS is an underlayer that is located between the segment S1 andthe body part 100. Further, the pressure transition system PTS mayinclude an auxetic-foam composite or alternative deformablemicrocellular structure, and have one or more walls of a stretchyfabric, which allow the system PTS to expand in the circumferentialand/or axial directions, so that the external basic pressure profile P1causes a deformation of the system PTS, and as a result an adjustedpressure profile P1 ^(adj) is exerted on the body part 100.

The pressure transition system PTS may also include drug containingpockets (here generally illustrated by means of white circles). In thiscase, the system PTS is also adapted to administer a transport of anydrug substance in these pockets to the body part 100, for instance inconnection with an applied basic pressure profile P1. The drug substancemay contain various topical agents for slow release application to thebody part 100. Such topical agents may soften or moisturize the tissuesin the body part 100 to prevent cracking and maintain or improve theoverall health of the patient's skin. Alternatively, the drug substancemay contain benzopyrones, flavonoids, coumarin, terpenses etc. for slowrelease into the underlying body part 100. Moreover, the drug substancemay be an antibacterial agent, which helps in preventing infection of awound site in the body part 100.

According to one embodiment of the invention, the drug substance is agel, which is adapted to perform a thermotherapy on the body part 100(e.g. a cryotherapy for pain relief, or a heat therapy to promote tissuehealing). If the actuator A1 is based on an active material thatrequires an electrolyte and if a thermotherapy of the body part 100 isdesired, it is preferable to let a gel based electrolyte play dual rollsin both operating the actuator A1 and accomplishing the cryotherapy.

FIG. 1 b shows a schematic cross-section view of a device according toone embodiment of the invention where the device includes (at least) twosegments S1 and S2. A first segment S1 at least partially encloses afirst portion B1 of a body part 100 and a second segment S2 at leastpartially encloses a second portion B2 of the body part 100. Thepressure transition system PTS is here adapted to redistribute pressureprofiles between the first and second segments S1 and S2. Specifically,this means that if the first segment S1 receives a control signal whichcauses the segment S1 to generate a first basic pressure profile P1, thepressure transition system PTS applies a first adjusted pressure profileP1 _(adj) to at least a part of the second portion B2 of the body part100. Correspondingly, if the second segment S2 receives a control signalwhich causes this segment S2 to generate a second basic pressure profileP2, the pressure transition system PTS applies a second adjustedpressure profile P2 _(adj) to at least a part of the first portion B1 ofthe body part 100. Hence, in response to control signals in respect ofthe segments S1 and S2 relatively smoothed-out, or fuzzy, pressureprofiles are applied to the body part 100. This is advantageous bothfrom a medical and a patient-comfort point-of-view.

According to one embodiment of the invention, the pressure transitionsystem PTS is adapted to apply a bias pressure profile to the body part,such that the body part 100 is exerted to an initial pressure profilealso before any of the basic pressure profiles P1 or P2 are applied. Thebias pressure profile may be attained passively due to the pressuretransition system PTS being stretchy. Then, the segments S1 and S2 mayoperate “on top of” this bias pressure profile to provide adjustmentsand/or dynamic therapies. Thereby, the pressure transition system PTSnot only redistributes the basic pressure profiles P1 or P2 but alsomodifies the magnitude of the average pressure. For example, thesegments S1 and S2 may apply basic pressure profiles P1 and P2 of 20mmHg to the pressure transition system PTS, which already applies 20mmHg to the body part 100. As a result, a pressure in the order of 40mmHg is applied to the body part 100.

As can be seen in the FIG. 1 b, at each body cross section enclosed bythe device, the pressure transition system PTS is positioned between afirst surface defined by the first and second segments S1 and S2, and asecond surface defined by the body part 100. Additionally, the pressuretransition system PTS extends over the first and second portions B1 andB2 of the body part 100. In order to further illustrate the function ofthe proposed pressure transition system PTS we now refer to FIG. 1 c.This figure shows a diagram wherein the horizontal axis indicates aposition along the body part 100 and the vertical axis reflects apressure towards the body part 100. A dashed line represents a desiredpressure P_(des) to t be applied to the body part 100. As can be seen,the pressure transition system PTS a comparatively even pressure Papproximately at the P_(des-)level along the entire extension of thepressure transition system PTS (i.e. also between and outside thesegments S1 and S2).

FIGS. 1 d and 1 e illustrate a situation corresponding to that shown inthe FIGS. 1 b and 1 c, wherein the first and second segments S1 and S2are form-fitted around the body part 100, however without anyintermediate pressure transition system PTS. Here, unacceptable pressurepeaks above the desired pressure P_(des) occur at several places,particularly at the edges of the segments S1 and S2. The FIG. 1 e alsoillustrates separate pressure curves P1 and P2 respectively, which arecaused by each individual segment S1 and S2 in the absence of thepressure transition system PTS.

FIG. 2 shows a perspective view of a device according to a firstembodiment of the invention. Here, two segments S1 and S2 are shown.However, according to the invention, the device may include any numberof segments larger than two. The pressure transition system PTS is atleast positioned between the first and second segments S1 and S2.Thereby, the pressure transition system PTS may bridge over pressureprofiles and tension forces from one segment to another, i.e. from S1 toS2, from S2 to S1, etc. Here, different degrees of coupling between thesegments may be attained depending upon which fiber directions that arechosen for a fabric used in the pressure transition system PTS.

As mentioned above, according to the invention, each segment S1 and S2includes an actuator A1 and A2 respectively. Here, the segments S1 andS2 include a respective strap member 240 and 250, and the actuators A1and A2 are located at one end of each segment. The actuators A1 and A2are further attached to the strap members 240 and 250, which at leastpartially enclose the body part 100. In response to control signals, theactuators A1 and A2 are adapted to pull the strap members 240 and 250,thus accomplish tension forces relative to the body part 100. Accordingto the invention, many different forms of actuators the segments S1 andS2 include a respective strap member 240 and 250, and the actuators A1and A2 are located at one end of each segment. The actuators A1 and A2are further attached to the strap members 240 and 250, which at leastpartially enclose the body part 100. In response to control signals, theactuators A1 and A2 are adapted to pull the strap members 240 and 250,thus accomplish tension forces relative to the body part 100. Accordingto the invention, many different forms of actuators may produce suchtension forces. For example bending, spring, wrinkle, bellows,laminates, friction drives, linear stack piezoceramic (or c-block) andknitted fiber actuators may be used.

Nevertheless, in response to a respective control signal, the actuatorsA1 and A2 of FIG. 2 adjust their morphology so that a tangentialmovement T of segments S1 and/or S2 occurs. As a result, a radialpressure is exerted on the body part 100. For energy efficiency reasons,it is preferable that the actuators A1 and A2 be adapted to maintaintheir adjusted morphologies also after that the control signals haveceased, i.e. that the control signals merely instigate the morphologychange.

According to a first alternative embodiment of the invention, thepressure transition system PTS is exclusively positioned between thesegments S1 and S2. This design is preferable if a very slim deviceprofile is important. However, according to a second alternativeembodiment of the invention, the pressure transition system PTS alsoextends underneath the segments S1 and S2. In this case it is furtherpreferable if the pressure transition system PTS has a low-frictionsurface towards the segments S1 and S2, so that smooth tangentialmovements of the segments' strap members are enabled.

According to this second alternative embodiment of the invention, thepressure transition system PTS may include sensor elements 210 and 220,which are adapted to register relevant parameters, and transmit datasignals reflecting these parameters to a control unit for analysis.

For example, the sensor elements 210 and 220 may be adapted to registerpressure, and in this case the elements can take the form of thin filmforce sensors (e.g. capacitive, piezoresistive, piezoelectric, varyingcontact or Quantum Tunneling Composite—QTC). If, on the other hand, thesensor elements 210 and 220 are intended to monitor the localcircumference of the body part 100, the sensor element 230 may insteadtake the form of a resistive strip, an interdigitated electrode withcontacts, or similar sensor which surrounds the body part 100. Thesensor elements 210 and 220 may also be responsible for measuringphysiological parameters, such as heart rate, galvanic skin response,electromyogram—EMG, blood oxygen levels, exudates extraction rates.

In the embodiment illustrated in FIG. 2, the pressure transition systemPTS includes a sensor element 230 that is adapted to register aparameter expressing an environmental condition in proximity to the bodypart 100, e.g. temperature, airflow, humidity or contamination. Namely,these types of environmental conditions may also influence what is anideal behavior of the proposed device. Thus, based on data signals fromthe sensor elements 210 and 220 and/or the sensor element 230, atreatment profile executed by the device may be adjusted.

FIG. 3 shows a perspective view of a device according to a secondembodiment of the invention. Here, each of a number of segments S1, S2,etc. at least partially encloses a body part 100. Moreover, the segmentsare arranged such that a portion of one segment S1 covers a portion of aneighboring segment S2, and so on. Thereby, analogous to the embodimentdescribed above with reference to FIG. 1 b, relatively smoothed-out, orfuzzy, pressure profiles may be applied to the body part 100 in responseto control signals in respect of the segments S1 and S2. Moreover, toredistribute these pressure profiles a pressure transition system PTS islocated between the segments and the body part 100. Preferably, thepressure transition system PTS has a low-friction surface towards thesegments S1 and S2, so that smooth tangential movements of the segmentsS1 and S2 are allowed relative to the pressure transition system PTS.

FIGS. 4 a-b show two cross-section views of one embodiment of theproposed pressure transition system PTS.

Here, the pressure transition system PTS includes a number ofcollapsible ribs 410 which are positioned between at least one segmentS1 and a particular portion of the body part 100 when the device isfitted on the body part 100. Preferably, a cover layer 420 separates theribs 410 from the body part 100. The ribs 410 extend along a generalcentral axis of the body part 100. Hence, in these cross-section views,we only see the section profile of the ribs 410. In response to acontrol signal, an actuator A1 of the segment S1 is adapted to cause atangential movement T of the segment S1 relative to the body part 100(see FIG. 4 b). In response to the movement T, in turn, the ribs 410 areadapted to fold, such that when folded the ribs 410 exert a radialpressure P on the particular portion of the body part 100.

FIGS. 5 a-b show two cross-section views of another embodiment of aproposed pressure transition system PTS. Also in this case, the pressuretransition system PTS is adapted to transform a tangential movement Tinto a resulting radial pressure P on a body part 100. Here, however,the pressure transition system PTS includes at least one flexiblechamber 510, which is positioned between at least one segment S1 and thebody part 100 when the device is fitted on the body part 100. Anactuator A1 of the segment S1 is adapted to cause the tangentialmovement T of the segment S1 relative to the body part 100 in responseto a control signal. The tangential movement T, in turn, deforms theflexible chamber 510, so that the chamber 530 causes a radial pressure Pon the body part 100, preferably via an underlayer 520. The chamber 510has at least one attachment point 530 to the segment S1. When thesegment S1 slides over the body part 100 the attachment point 530follows this movement, and the chamber 510 is compressed. The chamber510 may contain any flexible medium, such as a gas, a gel or a liquid.In any case, chamber 510 has elastic walls, which according to apreferred embodiment of the invention are made of an anisotropicmaterial. Thereby, the chamber 510 may be arranged relative to the bodypart 100 when the device is fitted thereto, such that the chamber 510 isrelatively stretchable in a circumferential direction of the body part100 and relatively stiff in a direction along a general central axis ofthe body part 100. Thus, the radial pressure P may be well distributedover the body part 100. At the same time, the pressure transition systemPTS can be soft in the circumferential direction, so that fit andpatient comfort is enhanced.

Generally, the tension-force to pressure transduction embodimentsillustrated in the FIGS. 4 a-b and 5 a-b may provide useful designswhenever a slim, robust and energy efficient device is desired.

FIG. 6 a shows a perspective view of another embodiment of the proposedpressure transition system PTS, which includes a number of protrusionsin the form of rigid ribs 620. These ribs 620 are adapted to bepositioned between at least one segment S1, S2 and S3 respectively and aparticular portion of the body part 100. The ribs 620 are adapted toextend along a general central axis of the body part 100 and to convertthe basic pressure profile of the segments S1, S2 and S3 into anon-uniform pressure profile to the particular portion of the body part100. Thus, a peak pressure ridge of the non-uniform pressure profile isproduced for each rib, and the pressure ridges are defined by thepositioning of the ribs 620 relative to the body part 100. Moreimportant, however, by means of the ribs 620 pressure profiles appliedby the segments S1, S2 and S3 are distributed across the body part 100.Preferably, the ribs 620 may be sewn into a soft backing material, sothat the entire structure can easily expand in the radial direction(e.g. to accommodate a wide range of patient limb sizes) while beingstiff in the axial direction (i.e. along the body part 100). Forillustrative purposes, the segments S1, S2 and S3 have here beenseparated more than what is normally preferable.

FIG. 6 b shows a perspective view of an alternative embodiment of theproposed pressure transition system PTS, where instead the protrusionsare cylindrical bulges 630. The bulges 630 are adapted to be positionedbetween at least one segment S1 and a particular portion of the bodypart when the device is fitted on the body part. Analogous to theabove-mentioned ribs, the bulges 630 are adapted to convert the basicpressure profile of the segment S1 into a non-uniform pressure profileto the particular portion of the body part. Here, however, each bulge630 causes a circular pressure peak. Such pressure peaks areparticularly suitable when treating lymphoedema.

FIG. 6 c shows yet another perspective view of a device according to oneembodiment of the invention. The device includes a number of segmentsS1, S2, . . . , Sn, which are arranged linearly along a body part 100,such as an arm or a leg. Analogous to the embodiment shown in FIG. 6 a,for illustrative purposes, the segments S1, S2 and S3 have also herebeen separated more than what is normally preferable. Nevertheless, eachsegment S1, S2, . . . , Sn is associated with a pressure transitionsystem PTS which encloses the body part 100 and has fiber directionsaccording to the curved lines. Moreover, the pressure transition systemsPTS overlap partially, such that some portions of the body part 100 arecovered by more than one pressure transition system PTS. For instance, amajority of the body part 100 may be covered by at least two differentpressure transition systems PTS. This configuration results in that anactivation of a first segment S1 causes a pressure to be applied toportions of the body part 100 which may also be pressurized via a secondsegment S2, and so on. Hence, smoothed-out, or fuzzy, pressure profilesmay be applied to the body part 100 in response to control signals C(i)in respect of the segments S1, S2, . . . , Sn. According to a preferredembodiment of the invention, a control unit 640 produces a respectivecontrol signal C(i) to each of segment S1, S2, . . . , Sn. Preferably,these control signals C(i) are distributed via a common signal deliverysystem 650. The control unit 640 is adapted to vary the control signalsC(i) over time, so that a treatment profile is implemented with respectto the body part 100. The treatment profile may involve producingrepeated cycles of variations between relatively high and relatively lowbasic pressure profiles by means of each segment S1, S2, . . . , Sn.

The treatment profile, in turn, may be adaptive in response to amanipulation signal that either is an external signal, or is produced bythe device itself. For example, as mentioned above with reference to theFIG. 2, one or more sensor elements in the segments S1, S2, . . . , Snmay transmit data signals R to the control unit 640. Consequently, themanipulation signal can be based on such data signals R, so that thetreatment profile depends on a current state of the body part 100 and/orthe current environmental conditions. Moreover, the data signals R mayreflect a patient's posture. Therefore, according to the invention, itis rendered possible to adapt the treatment profile to the posture. Forexample, if the segments S1, S2, . . . , Sn are fitted around thepatient's leg, they may be completely relaxed when the patient is lyingdown (e.g. apply a pressure profile in the range 0-10 mmHg), apply arelatively low graduated pressure profile (e.g. in the range 0-40 mmHg)when the patient is standing up and apply a relatively high graduatedpressure profile (e.g. in the range 0-60 mmHg) when the patient issitting.

According to preferred embodiment of the invention, the control signalsC(i) are electrical signals, and the segments S1, S2, . . . , Sn haveactuators whose morphology is electrically adjustable. Moreover, theadjustments of the actuator morphologies are preferably only instigatedby the control signals C(i) (i.e. no control signal is necessary tomaintain an adjusted morphology). Naturally, according to the invention,the control unit 640 may be connected to any of the proposed segmentsand pressure transition systems, i.e. not only the elements ofembodiment shown in FIG. 6 c.

FIG. 7 shows a cross-section view of the pressure transition system PTSaccording to one embodiment of the invention, where the pressuretransition system PTS includes a number of moisture passages 710schematically illustrated as tubes with internal flanges. Each moisturepassage 710 is adapted to receive exudates from the body part 100, andthus assist in keeping the skin relatively dry.

According to one preferred embodiment of the invention, the pressuretransition system PTS includes one or more liquid receptacles 715, andthe moisture passages 710 are adapted to transport any received exudatesfrom the body part 100 this/these receptacle/s 715 concomitantly withrepeating cycles of a treatment profile executed by means of segments S1and S2 associated with the pressure transition system PTS. Preferably,the moisture passages 710 and liquid receptacles 715 are accomplished bymeans of air pockets of an open-celled foam. Thus, these elements'physical configuration is quite dissimilar from what is illustrated inFIG. 7, however their function is identical thereto.

According to another preferred embodiment of the invention, the pressuretransition system PTS includes a number of air channels 720 which areadapted to allow air to pass to the body part 100. Analogous with themoisture passages 710 and the liquid receptacles 715, the air channels720 may also be adapted to operate concomitantly with the repeatingcycles of the treatment profile executed by means of the segments S1 andS2, so that air is exchanged more efficiently between the body part 100and a local environment outside thereof. Moreover, open-celled foamopenings may also constitute the air channels 720.

FIG. 8 a illustrates the basic morphology of a planar field activatedEAM-based actuator 805. Two essentially plate-shaped electrodes 810 and811 are here separated by means of an EAM piece 820. When an electricfield is applied over the EAM piece 820, i.e. when one of the electrodes810 is connected to a first polarity, say a positive voltage, and theother electrode 820 is connected to a second polarity, say a negativevoltage, the EAM piece 820 undergoes a shape change, for instance bybecoming thinner and longer. This situation is shown in FIG. 1 b.

The shape change of the EAM 820 arises due to a variety of physicalreasons when a non-zero charge is supplied to the electrodes 810 and811, for example via a power supply or a control signal. In response tosuch a charge, the EAM 820 attempts to undergo a change in shape. Themagnitude of the shape change depends on the material properties of theEAM 820, the frequency of the charge application/removal and mechanicalboundary conditions of the material. Typically, the change in shape isrelated to the amount of charge accumulated on the surroundingelectrodes 810 and 811.

In all dielectric materials, charge accumulation on adjacent electrodescreates mechanical stress in the material due to attraction andrepulsion of the adjacent charges. Such stresses are referred to asMaxwell stresses. In soft materials, e.g. dielectric elastomers andgels, these stresses are sufficient to cause a significant shape changeof the material.

Also in crystallographic materials, such as ceramics and ferroelectricpolymers, an appreciable change in properties occurs with shape changeof the material. This phenomenon is referred to electrostriction. Due toelectrostrictive effects, the material will strive at changing the shapein response to an applied charge (in addition to Maxwell stresseffects). Furthermore, an initial polarization may be frozen into someEAMs during manufacture. In materials capable of maintaining an initialpolarization, the applied charge elicits a change in shape referred toas the reverse piezoelectric effect. Piezoelectric effects generallydemonstrate a linear relationship between material strain and resultingelectric field. Electrostrictive effects, on the other hand, generallydemonstrate a quadratic relationship between material strain and appliedelectric field under linear boundary conditions. Under certaincircumstances, these effects are reversible. Therefore, when theelectroactive material undergoes a shape change, an electrical responseoccurs. This allows electric energy to be captured from the movingelectroactive material. It also enables for the materials to operate assensors.

Another important property of the EAMs is that a deformation (i.e. achanged morphology) resulting from an applied charge will be maintainedif the electrodes are left open-circuited. Nevertheless, due to slightconductive effects, the thus separated charges will slowly leak throughthe EAM. Therefore, in practice, some replenishment/maintenance chargeis necessary to top up the existing charge, and maintain a desireddeformation.

FIGS. 9 a and 9 b illustrate top- and side views respectively of themorphology of a cylindrical field activated EAM-based actuator 905,which may be used to apply pressure according to the invention. Here, afirst cylindrical electrode 910 is enclosed by an EAM piece 920. Asecond electrode 911, in turn, encloses the EAM piece 920. FIG. 9 cshows a side-view corresponding to the FIG. 9 b, however where the firstelectrode 910 is connected to a positive voltage and the secondelectrode 911 is connected to a negative voltage. In similarity with theexample shown in FIG. 8 b, the EAM piece 920 contracts in response tothe applied electric field, and the actuator's 905 diameter decreaseswhile its length increases.

A multilayer cylindrical actuator of the type shown in the FIGS. 9 a and9 b may be accomplished straightforwardly by wrapping a planar actuatoraround a spring, or tube-like mandrel. Thereby, a compact, multilayered(i.e. high strength) tubular actuator can be cost effectively createdfrom a simple planar starting geometry.

FIG. 10 a shows a schematic side-view of a field activated EAM-basedactuator 1005 of multilayer (or stacked) type, which may be usedaccording to the present invention. Many interconnected layers of EAM1020 are here alternately separated by a first essentially planarelectrode 1010 and a second essentially planar electrode 1011. FIG. 10 billustrates the case when an electric field is applied across theelectrodes 1010 and 1011. As can be seen, this again results in acontraction of the EAM 1020. However, a material expansion may insteadresult if for example a piezoceramic is used as the EAM 1020. In anycase, by means of a stacked-type of actuator, a substantial mechanicalamplification can be achieved. Triple layer actuators (or so-calledbimorph cantilever actuators) can be formed by means of two EAM piecesseparated by a supporting element, where opposite electric fields areapplied to the EAM pieces. Thereby, the actuator can be controlled tobend in two different directions depending on which EAM piece that isactivated, or the polarities applied to each of the EAM pieces.

Moreover, according to the invention, layers of passive materials mayalso be laminated along with the active material. These extra layers areoften useful when interfacing with the surroundings, improving adhesionbetween adjacent active material layers, and creating favorable residualstresses in the active material during manufacturing.

FIG. 11 a shows a schematic side view of a field activated EAM-basedactuator 1105 of C-block type, which also may be used according to theinvention. In each block of this actuator 1105 a curved-profile laminatematerial 1130 adjoins an EAM piece 1120, which likewise has a curvedprofile. The general curved profile of each block amplifies the motionof the basic movement of the EAM piece 1120. Two or more of these blocksmay be connected in series with one another to accomplish a furtheramplification effect. When an electric field is applied between therespective EAM piece 1120 and the laminate material 1130, the EAM piece1120 contracts according to what is illustrated in FIG. 11 b.

FIG. 12 a illustrates the morphology of a field activated EAM-basedactuator 1205 of bubble type according to one embodiment of theinvention. Here, an EAP membrane 1220, shaped as a truncated sphere (orsimilar bubble-like shape), is attached to a rigid mounting material1230. According to one embodiment of the invention, a pneumatic pressurebias is used to create the convex shape of the EAP membrane 1220. Anelectric field across the EAP membrane 1220 causes the membrane 1220 toexpand from its initial (inactivated) morphology. FIG. 12 b illustratessuch an activated state. For example, such actuators can be used tocreate localized pressure points on the body.

FIG. 13 shows a field activated EAM-based actuator 1305 of cymbal typeaccording to one embodiment of the invention. Multilayered EAM strips1320 are here located between two flexible, cymbal-shaped interfaceelements 630. When activated, i.e. in response to an electric fieldacross the EAM strips 1320, the strips 1320 contract or expand andpull/push the interface elements 1330 inwards or outwards as indicatedby the arrows. Thereby, a pressure can be applied via first and secondcontact surfaces 1335 a and 1335 b respectively, which are located atthe distal ends of the interface elements 1330. Preferably, theinterface elements 1330 are flexible and the EAM strips 1320 areoriented with their longest sides parallel to a symmetry axis of theinterface elements 1330, i.e. according to a layered structure asillustrated in the FIG. 13.

FIG. 14 a shows a perspective view of another cymbal type of fieldactivated EAM-based actuator 1405, which may be used in a deviceaccording to the invention. FIG. 14 b shows a sectional side view ofthis actuator 1405. Here, two interface surfaces 1435 a and 1435 b areinterconnected by means of a number of flexible members 1430, which inturn, are attached to an EAM piece 1420 located between the interfacesurfaces 1435 a and 1435 b. Thereby, upon activation of the actuator1405, so that the EAM piece 1420 expands E, the interface surfaces 1435a and 1435 b move toward one another D_(E) (essentially along theirsymmetry axes). Analogous thereto, upon activation of the actuator 1405,so that the EAM piece 1420 instead contracts C, the interface surfaces1435 a and 1435 b are separated from one another D_(C) (essentiallyalong their symmetry axes). Hence, a desired pressure can be createdtowards a body part through transformation of the basic materialmovement of the EAM piece 1420.

FIG. 15 a illustrates a basic morphology of an ionic EAM-based actuator1505 according to one embodiment of the invention. Ionic electroactivematerials are characterized in that actuator systems based on themcontain ions and that migration of these ions occurs under the influenceof voltage potentials applied between electrodes 1510 and 1520 withinthe system. The ion migration, in turn, causes swelling or shrinking ofthe actuator. There are many designs based on the concept ofelectrically induced ionic migration. Some exemplary designs, which maybe used according to the invention will be discussed below withreference to FIGS. 16 to 17.

In similarity with field activated EAMs, ionic electroactive materialreactions are reversible. Therefore, actuators based on ionic EAMs canalso be used as various types of sensors and energy accumulators.

Returning now to FIG. 15 a, conducting polymer actuators generally havean ion reservoir, such as an electrolyte 1550 (in the form of a liquid,a gel or a solid), which separates a working electrode 1510 and acounter electrode 1520. The working electrode 1510 usually includes theEAM (i.e. the conducting polymer). Also the counter electrode 1520 mayinclude an EAM, however usually different from the EAM of the workingelectrode 1510. The counter electrode 1520 may thus include a naturallyconducting material, such as a metal or a graphite film. Moreover, thecounter electrode 1520 may be made from nanocomposites, fabricated tohave both high conductivity and low mechanical stiffness.

The working electrode 1510 may likewise include a composite of activematerials and passive materials. In such cases, the passive materialsare normally included to improve the conductive properties of theworking electrode 1510 while not impeding movement of the electrodeduring operation. Also here, conductive nanocomposites represent aviable option for lamination with the conducting polymer material.

In some cases, a reference electrode 1530 is present in the electrolyte1550 to ensure that desired voltage potentials are maintained atappropriate levels at the other electrodes 1510 and 1520 duringoperation of the actuator 1505. When the voltage potentials of theelectrodes 1510 and 1520 are varied, the electroactive polymer canundergo oxidation or reduction reactions. Large electric fields aregenerated at the interfaces between the electrodes 1510 and 1520respectively and the electrolyte 1550. This causes ion migration acrossthe interfaces. Ions within the EAM can initiate conformational changeof the crystallographic structures of the material, or they may take upinterstitial spaces in the material and cause it to swell. If ions areextracted from the EAM in the working electrode 1510 due to migration,the working electrode 1510 may shrink. Depending on the counterelectrode material, reactions at the electrode 1520 may or may notresult in another usable shape change in respect of this electrode. Thedetails of the entire actuator system (such as the specific EAMs,electrolyte and counter electrode properties) together dictate the finalresponse of the system during operation.

FIG. 15 b illustrates a situation where a positive voltage has beenapplied to the working electrode 1510 and a negative voltage has beenapplied to the counter electrode 1520. As a result, the workingelectrode 1510 extends while its width decreases. For improved expansionproperties, the working electrode 1510 may be designed as a composite ofconductive helical supporting structure encapsulated by the EAM (notshown here). A possible extension of the counter electrode 1520(resulting from an included EAM) is illustrated by means of a dashedprofile.

In the case of carbon nanotubes, the presence of carbon nano-tubesdramatically increases the surface area of the electrode. This, in turn,increases the strength of the electromagnetic field during a reductionor oxidation process. Consequently, an increased ion migration occursand therefore an amplified mechanical response can be obtained. Theformation of gas can arise intimately with the electrode during areaction (often due to electrolysis of water). Of course, the expansionof such gases may also result in an increased response.

FIG. 16 a illustrates the morphology of a bilayer ionic EAM-basedactuator 1605 according to one embodiment of the invention. Here, aworking electrode 1610 of a conductive polymer (EAP) adjoins anon-conducting polymer backing element 1620, which mainly functions as amechanical support to the actuator laminate of the working electrode1610. A counter electrode 1611 is arranged physically separated fromboth the working electrode 1610 and the backing element 1620. Theworking electrode 1610 and the EAP 1620 are attached to an anchor member1630, and all the elements 1610, 1620 and 1611 are surrounded by anelectrolyte 1640. FIG. 16 b shows a situation when a negative voltagehas been applied to the working electrode 1610 and a positive voltagehas been applied to the counter electrode 1611, causing the conductivepolymer to contract, and as a result, the entire working electrode andbacking element system to bend.

FIG. 17 a illustrates the morphology of a triple ionic layer EAM-basedactuator 1705 according to one embodiment of the invention, which issimilar in morphology to the actuator design of FIGS. 16 a and 16 b.Here however, two conductive polymer electrodes 1710 and 1711 areseparated by means of a non-conducting polymer element 1720. All theelements 1710, 1711 and 1720 are attached to an anchor member 1730, andmay or may not be surrounded by an electrolyte. Namely, thenon-conducting polymer element 1720 may include a solid polymerelectrolyte, and thus forego the need for a surrounding electrolyte. Insuch a case, the elements 1710, 1711 and 1720 must be encapsulated toprevent evaporation of the electrolyte. FIG. 17 b illustrates how theactuator 1705 upon activation can be controlled to flex in differentdirections .SIGMA₁ and .SIGMA₂ depending on the polarity of a voltageapplied between the electrodes 1710 and 1711. In this case, the actuator1705 bends upwards .SIGMA₁ in response to a negative voltage potentialconnected to the first electrode 1710 and a positive voltage potentialconnected to the second electrode 1711. Correspondingly, the actuator1705 would bend downwards .SIGMA₁ in response to opposite voltagepotentials.

In addition to the actuator morphologies shown in the FIGS. 15 to 17,the actuators according to the invention may take the form of fibers,fabrics or strips based on the basic concept ionic EAM-based actuators.Naturally, according to the invention, the basic actuator morphologiesmay be combined and be arranged in arrays to produce more advancedactuators.

FIG. 18 a shows a side view of an inactivated conducting polymeractuator A1 according to one embodiment of the invention. FIG. 18 bshows a corresponding top view. This actuator A1 operates according tothe basic principle described above with reference to the FIGS. 15 a and15 b. Nevertheless, both a working electrode 1810 and a counterelectrode 1820 include a conductive polymer. An electrolyte 1830 isenclosed by these electrodes 1810 and 1820. The actuator A1 is activatedby means of an applied voltage between a first electrode tab 1810 a anda second electrode tab 1810 b. When such a voltage is applied, theworking electrode 1810 contracts and the counter electrode 1820 expands.As a result, the actuator A1 both contracts in plane and expands out ofthe plane according to the top-view illustration of FIG. 18 c.

FIG. 19 a illustrates a side view of a segment in a device according toone embodiment of the invention, which includes a number of actuators A1₁, A1 ₂, and A1 ₃ of the type shown in the FIGS. 18 a-c. Theoretically,one actuator is sufficient to exert an external pressure to a body part100 by means of the proposed device. However, for improved effect aplurality of actuators may be used. If so, the actuators aremechanically connected to one another to at least partially enclose thebody part 100, such as the limb of a patient, in a form-fitting manner.Depending on the number of actuators and the range of motion of eachactuator A1 ₁, Al₂, and A1 ₃, the device may be capable of completelydisengaging the body part 100 at the conclusion of treatment. In thiscase, a strap 1910 (or equivalent) transmits actuator forces around thebody part 100 and fixates the actuators A₁, A1 ₂, and A1 ₃ to the bodypart 100. In other cases, the strap 1910 may contain a variety oflocking mechanisms to assist with the removal of the device from thepatient after treatment, or assist with size adjustment of the device tothe patient.

Here, a first actuator A1 ₁ includes a first working electrode 1810 ₁and a first counter electrode 1820 ₁; a second actuator A1 ₂ includes asecond working electrode 1810 ₂ and a second counter electrode 1820 ₂;and a third actuator A1 ₃ includes a third working electrode 1810 ₃ anda third counter electrode 1820 ₃. Further, the first actuator A1 ₁ isconnected to the second actuator A1 ₂, which in turn, is connected tothe third actuator A1 ₂ according to the configuration of FIG. 19 a.Strap members 1910 are attached to the first and third actuator A1 ₁ andA1 ₃ to fixate the device to the body part 100. The electrode tabs ofeach actuator A1 ₁, A1 ₂, and A1 ₃ are also electrically connected to anelectric power source, so that the actuators can be activated by meansof electric charges being supplied to their electrodes. However, forreasons of a clear presentation, this is not shown in the FIG. 19 a.

Preferably, a pressure transition system PTS is arranged as an interfacebetween the actuators A1 ₁, A1 ₂, and A1 ₃ and the body part 100. Thepressure transition system PTS is adapted to redistribute a basicpressure profile of the actuators A1 ₁, A1 ₂, and A1 ₃, such that whenthe actuators are activated, an adjusted pressure profile different fromthe basic pressure profile is applied to the body part 100. Thereby, asmoother (or more fuzzy) pressure profile P can be applied to the bodypart, which is desirable in many medical applications.

According to another preferred embodiment of the invention, any voidsbetween the actuators A1 ₁, A1 ₂, and A1 ₃ and the pressure transitionsystem PTS are filled with an open-celled foam (not shown). Namely, thisfurther assists in redistributing pressure from the actuators A1 ₁, A1₂, and A1 ₃ to the body part 100 without overly affecting the breathability of the device.

FIG. 19 b illustrates a situation when all the actuators A1 ₁, A1 ₂, andA1 ₃ are activated, and therefore each actuator A1 ₁, A1 ₂, and A1 ₃ hasadapted morphology equivalent to what is shown in the FIG. 18 c. As aresult, a pressure profile P is applied to the body part 100, and as afurther consequence the body part 100 is normally compressed/deformed(which is here illustrated by means of a reduced cross-sectiondiameter). If, however, the body part 100 were very stiff, and thereforewould not deform under the pressure profile P applied, the actuators A1₁, A1 ₂, and A1 ₃ and the strap members 1910 would exert tensile forcesF around the body part 100 without undergoing the large deformationsdepicted in the FIG. 19 b.

FIGS. 20 a and 20 b show side views of a bending actuator A2 accordingto one embodiment of the invention. Preferably, this type of actuator A2includes a bending member 2010 of field activated EAM-type. The bendingmember 2010 is adapted to operate against a local pressure transitionsystem PTS′ and an over layer 2030, for instance in the form of anappropriate interfacing fabric. An elastic back plate side of thebending member 2010 faces the over layer 2030. FIG. 20 a illustrates aninactivated state of the actuator A2, while FIG. 20 b illustrates anactivated state. As can be seen, when activated the bending member 2010pushes the over layer 2030 away from the local pressure transitionsystem PTS′. This leads to tensile forces F in the over layer 2030,which according to the invention may be converted into a desiredpressure profile applied to a body part.

FIG. 21 a shows a side view of a segment in a device according to oneembodiment of the invention, which includes a number of actuators A2 ₁and A2 ₂ of the type shown in the FIGS. 20 a and 20 b. In theconfiguration shown, the number of actuators is increased to accommodatea wider range of available motion, and to more evenly distributepressure to a curved body part 100. If an increase pressure is desired,two or more actuators may be applied in parallel, i.e. be stacked, suchthat the actuators a layered on top of one another. Alternatively,multilayered laminates within each actuator element of an actuator arraymay be thickened. Nevertheless, for illustrative purposes only twoactuators A2 ₁ and A2 ₂ are shown here. The actuators A2 ₁ and A2 ₂ arelocated next to one another and have a common over layer 2110 (comparewith 2030 in the FIGS. 20 a and 20 b). Preferably, the over layer 2110has at least one attachment point 2120 between the actuators A2 ₁ and A2₂. Thereby, when activated, each actuator A2 ₁ and A2 ₂ contributesmaximally to the generation of a pressure towards the body part 100.Moreover, in addition to the local systems of each actuator, a pressuretransition system PTS is preferably arranged as an interface between theactuators A1 ₁ and A1 ₂ respectively and the body part 100. Such apressure transition system PTS is adapted to redistribute a basicpressure profile of the actuators A1 ₁ and A1 ₂, so that when theactuators are activated, an adjusted pressure profile different from thebasic pressure profile is applied to the body part 100. Thereby, asmoother (or more fuzzy) pressure profile P can be applied to the bodypart, which is desirable in many medical applications.

In similarity with the FIG. 19 b, FIG. 21 b shows a situation when theactuators A1 ₁ and A1 ₂are activated, and a pressure profile P isapplied to the body part 100. Normally, this leads to acompression/deformation of the body part 100 (which is here illustratedby means of a reduced cross-section diameter). If, however, the bodypart 100 were very stiff, and therefore would not deform under thepressure profile P applied, yet the over layer 2110 would still exerttensile forces F around the body part 100.

For proper function, the outer layer 2110 should be made of a rigid andstrong fabric, so that it does not stretch appreciably during activationof the actuators A2 ₁ and A2 ₂. Therefore, the outer layer 2110 ispreferably a knitted anisotropic material, which includes fibers (e.g.of Kevlar) that are strong in the circumferential direction (i.e. aroundthe body part 100), and relatively soft in the axial direction (i.e.along the body part 100). Moreover, the outer layer 2110 fabricpreferably has an open weave to ensure that the breath ability of thedevice is not compromised.

FIG. 22 shows a side view of a device according to one embodiment of theinvention for exerting an external pressure to a human body part 100.The device includes segments S1, S2 and S3, which are adapted to atleast partially enclose the body part 100 in a form-fitting manner. Eachsegment S1, S2 and S3 contains a controllable active-material basedactuator A (e.g. of the type illustrated in the FIGS. 21 a and 21 b)that is adapted to cause the segment to apply a pressure profile to thebody part 100 in response to a control signal C(i). The device may alsoinclude a pressure transition system PSS, which is adapted toredistribute a basic pressure profile produced by the segments S1, S2and S3 into an adjusted pressure profile which is different from thebasic pressure profile. Thus, the pressure transition system PSSaccomplished a relatively smoothed-out, or fuzzy, pressure profile to beapplied to the body part 100. This is advantageous both from a medicaland a patient-comfort point-of-view. The pressure transition system PSS,in turn, preferably includes an auxetic-foam composite or other materialhaving a deformable microcellular structure.

FIGS. 23-26 illustrate examples of therapeutic garments 2300, 2400, 2500and 2600 including the proposed device.

FIG. 23 shows a leg garment 2300, where a plurality of segments S1, S2,. . . , Sn are adapted to enclose both the upper and the lower part of apatients leg. An extensive pressure transition system PTS is adapted toredistribute basic pressure profiles generated by the segments S1, S2, .. . , Sn, so that the entire leg is exerted to adjusted pressureprofiles, for example also at joint portions of the leg that are notcovered by any segments.

FIG. 24 shows an arm garment 2400, where a plurality of segments S1, S2,. . . , Sn are adapted to enclose a patient's forearm and over arm. Alsohere an extensive pressure transition system PTS is adapted toredistribute basic pressure profiles generated by the segments S1, S2, .. . , Sn. Thereby, for instance, an elbow portion which for flexibilityreasons is not covered by segments may be exerted to pressure.Additionally, the pressure transition system PTS is adapted to extendover the patient's hand in the form of a compression glove 2410, so asto prevent lymphatic fluids from pooling in the hand.

FIGS. 25 and 26 show garments 2500 and 2600 for exerting externalpressures to a patient's foot and hand respectively. In both these casesa plurality of segments S1, S2, . . . , Sn are adapted to enclose a saidextremities, and a pressure transition system PTS is adapted toredistribute basic pressure profiles generated by the segments S1, S2, .. . , Sn. Thus, basic pressure profiles may be smoothed out and alsoportions which are not covered by segments may be pressurized.

The term “comprises/comprising” when used in this specification is takento specify the presence of stated features, integers, steps orcomponents. However, the term does not preclude the presence or additionof one or more additional features, integers, steps or components orgroups thereof.

The invention is not restricted to the described embodiments in thefigures, but may be varied freely within the scope of the claims.

What is claimed:
 1. A device for exerting an external pressure to aperson's limb, the device comprising: at least two segments of which afirst segment is adapted to at least partially enclose a first portionof the person's limb in a form-fitting manner and a second segment isadapted to at least partially enclose a second portion of the person'slimb in a form-fitting manner, each of the at least two segmentscontaining an electroactive-material-based actuator which is adapted toreceive an electrical control signal and in response thereto adjust theactuator's morphology so as to in the absence of any intermediatecomponent between the actuator and the person's limb cause the segmentto apply a basic pressure profile to the person's limb in directresponse to the electrical control signal; and a pressure transitionsystem comprising an underlayer and one or more pressure redistributionelements which is adapted to be positioned between a first surfacedefined by the first and second segments and a second surface defined bythe person's limb, wherein the pressure transition system extends overthe first and second portions of the person's limb when the device isfitted on the person's limb, and further wherein the pressure transitionsystem has such mechanical properties that the pressure transitionsystem is adapted to redistribute the basic pressure profiles betweenthe first and second segments via the one or more pressureredistribution elements, in such manner that a control signal in respectof the first segment causes the pressure transition system to apply afirst adjusted pressure profile to at least a part of the second portionof the person's limb, a control signal in respect of the second segmentcauses the pressure transition system to apply a second adjustedpressure profile to at least a part of the first portion of the person'slimb, and each of the first adjusted pressure profile and the secondadjusted pressure profile being different from each of a first basicpressure profile of the first segment and a second basic pressureprofile of the second segment.
 2. The device according to claim 1,wherein a change of said morphology is instigated by the electricalcontrol signal, and each of said actuators is adapted to maintain a thuschanged morphology on the basis of an electrical control signalsupplying charge replenishment to the actuator.
 3. The device accordingto claim 1, wherein the pressure transition system is adapted to bepositioned between the first and second segments when the device isfitted on the person's limb.
 4. The device according to claim 1, whereinthe pressure transition system has a low-friction surface towards thefirst and second segments, and said surface is adapted to allow a smoothtangential movement of the first and second segments relative to thepressure transition system.
 5. The device according to claim 1, whereinthe first and second segments are arranged such that a portion of thefirst segment covers a portion of the second segment when the device isfitted on the person's limb.
 6. The device according to claim 1, whereinthe one or more pressure redistribution elements of the pressuretransition system comprises a number of collapsible ribs adapted toextend along a general central axis of the person's limb and bepositioned between at least one of said segments and a particularportion of the person's limb when the device is fitted on the person'slimb, an actuator of each of said at least one segment is adapted tocause a tangential movement of said at least one segment relative to theperson's limb, and the collapsible ribs are adapted to fold in responseto said movement such that when folded the ribs exert a radial pressureon the particular portion of the person's limb.
 7. The device accordingto claim 1, wherein the one or more pressure redistribution elements ofthe pressure transition system comprises at least one flexible chamberadapted to be positioned between at least one of said segments and aparticular portion of the person's limb when the device is fitted on theperson's limb, an actuator of each of said at least one segment isadapted to cause a tangential movement of said at least one segmentrelative to the person's limb, and the at least one flexible chamber isadapted to transform said movement into a resulting radial pressure onthe particular portion of the person's limb.
 8. The device according toclaim 7, wherein the at least one flexible chamber has an elastic wallof an anisotropic material, the at least one chamber is adapted to bearranged relative to the person's limb when the device is fitted on theperson's limb such that the at least one chamber is relativelystretchable in a circumferential direction of the person's limb andrelatively stiff in a direction along a general central axis of theperson's limb.
 9. The device according to claim 1, wherein the one ormore pressure redistribution elements of the pressure transition systemcomprises a number of protrusions adapted to be positioned between atleast one of said segments and a particular portion of the person's limbwhen the device is fitted on the person's limb, said protrusions areadapted to convert the basic pressure profile of said at least onesegment into a nonunifoun pressure profile to the particular portion ofthe person's limb.
 10. The device according to claim 9, wherein saidprotrusions comprise at least one rigid rib adapted to extend along ageneral central axis of the person's limb and be positioned between atleast one of said segments and a particular portion of the person's limbwhen the device is fitted on the person's limb, and a respective peakpressure ridge of the nonuniform pressure profile is defined by apositioning of each of the at least one rib relative to the person'slimb.
 11. The device according to claim 1, wherein the device comprisesa control unit adapted to produce a respective control signal to each ofsaid segments, and the control unit is adapted to vary the controlsignal over time to implement a treatment profile with respect to theperson's limb.
 12. The device according to claim 1, wherein thetreatment profile involves applying gradually varying pressure profilesto the person's limb via said segments.
 13. The device according toclaim 11, wherein the treatment profile involves producing repeatedcycles of variations between relatively high and relatively low basicpressure profiles by means of each of said segments.
 14. The deviceaccording to claim 11, wherein the treatment profile involves producingquasi-static pressure profiles by means of said segments.
 15. The deviceaccording to claim 1, wherein the pressure transition system comprises anumber of air channels adapted to allow air to pass to the person'slimb.
 16. The device according to claim 15, wherein the air channels areadapted to exchange air between the person's limb and a localenvironment outside the device concomitantly with said repeating cycles.17. The device according to claim 11, wherein the pressure transitionsystem comprises at least one sensor element adapted to register aphysiological parameter of the person's limb, and transmit a data signalreflecting this parameter to the control unit.
 18. The device accordingto claim 11, wherein the pressure transition system comprises at leastone sensor element adapted to register a parameter expressing anenvironmental condition in proximity to the person's limb, and transmita data signal reflecting this parameter to the control unit.
 19. Thedevice according to claim 17, wherein the treatment profile is adaptivein response to at least one manipulation signal.
 20. The deviceaccording to claim 19, wherein at least one of the at least onemanipulation signal is based on at least one of said data signals. 21.The device according to claim 1, wherein the pressure transition systemcomprises at least one pocket adapted to contain a drug substance andadminister a transport of this substance to the person's limb.
 22. Thedevice according to claim 1, wherein at least one of said actuatorscomprises an electroactive polymer.
 23. The device according to claim 1,wherein at least one of said actuators comprises an electroactiveceramic.
 24. The device according to claim 22, wherein at least one ofsaid actuators comprises a field activated electroactive material. 25.The device according to claim 22, wherein at least one of said actuatorsis adapted to operate based on at least one of Maxwell stress effects,electrostrictive effects and piezoelectric effects.
 26. The deviceaccording to claim 22, wherein the electroactive polymer is electricallyisolated from the person's limb.
 27. The device according to claim 26,further comprising a pressure transition system arranged so as toelectrically isolate the electroactive polymer from the person's limb.28. The device according to claim 22, wherein at least one of saidactuators comprises an ionic electroactive material.
 29. The deviceaccording to claim 22, wherein at least one of said actuators comprisesa conducting polymer.
 30. A therapeutic garment adapted to cover atleast the person's limb, wherein the garment comprises at least onedevice according to claim 1.